A power actuator system is an option used to power open and close movable panels such as the lift gate or hinged/sliding access doors on certain passenger vehicles, vans and light trucks. The vehicle's computer module can be programmed to control the opening and closing of the lift gate. However, the computer module requires certain information about the lift gate so that the lift gate speed can be controlled and obstacles in the path of the lift gate may be detected. In certain vehicles, the computer module also needs to know the full open position of the lift gate.
Current designs of power lift gate systems typically use a motor speed sensing device to send information to the vehicle computer module. The vehicle's computer module then calculates the lift gate speed and position from that information. If the power to the motor speed sensing sensor is turned off, the position of the lift gate is then unknown. In other current designs and applications, additional switches may be required to detect full open and full closed positions.